[llvm-commits] [llvm] r72872 - in /llvm/trunk/lib: CodeGen/SelectionDAG/DAGCombiner.cpp CodeGen/SelectionDAG/SelectionDAG.cpp Transforms/Scalar/InstructionCombining.cpp

[Dan Gohman]

Author: djg
Date: Thu Jun  4 12:12:12 2009
New Revision: 72872

URL: http://llvm.org/viewvc/llvm-project?rev=72872&view=rev
Log:
Don't do the X * 0.0 -> 0.0 transformation in instcombine, because
instcombine doesn't know when it's safe. To partially compensate
for this, introduce new code to do this transformation in
dagcombine, which can use UnsafeFPMath.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=72872&r1=72871&r2=72872&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Jun  4 12:12:12 2009
@@ -4019,6 +4019,9 @@
   // fold (fmul A, 0) -> 0
   if (UnsafeFPMath && N1CFP && N1CFP->getValueAPF().isZero())
     return N1;
+  // fold (fmul A, 0) -> 0, vector edition.
+  if (UnsafeFPMath && ISD::isBuildVectorAllZeros(N1.getNode()))
+    return N1;
   // fold (fmul X, 2.0) -> (fadd X, X)
   if (N1CFP && N1CFP->isExactlyValue(+2.0))
     return DAG.getNode(ISD::FADD, N->getDebugLoc(), VT, N0, N0);

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=72872&r1=72871&r2=72872&view=diff

==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Thu Jun  4 12:12:12 2009
@@ -2807,16 +2807,19 @@
     case ISD::ADDC:
     case ISD::ADDE:
     case ISD::SUB:
-    case ISD::FADD:
-    case ISD::FSUB:
-    case ISD::FMUL:
-    case ISD::FDIV:
-    case ISD::FREM:
     case ISD::UDIV:
     case ISD::SDIV:
     case ISD::UREM:
     case ISD::SREM:
       return N2;       // fold op(arg1, undef) -> undef
+    case ISD::FADD:
+    case ISD::FSUB:
+    case ISD::FMUL:
+    case ISD::FDIV:
+    case ISD::FREM:
+      if (UnsafeFPMath)
+        return N2;
+      break;
     case ISD::MUL:
     case ISD::AND:
     case ISD::SRL:

Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=72872&r1=72871&r2=72872&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Thu Jun  4 12:12:12 2009
@@ -2585,7 +2585,9 @@
   bool Changed = SimplifyCommutative(I);
   Value *Op0 = I.getOperand(0);
 
-  if (isa<UndefValue>(I.getOperand(1)))              // undef * X -> 0
+  // TODO: If Op1 is undef and Op0 is finite, return zero.
+  if (!I.getType()->isFPOrFPVector() &&
+      isa<UndefValue>(I.getOperand(1)))              // undef * X -> 0
     return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
 
   // Simplify mul instructions with a constant RHS...
@@ -2612,16 +2614,14 @@
                  ConstantInt::get(Op0->getType(), Val.logBase2()));
       }
     } else if (ConstantFP *Op1F = dyn_cast<ConstantFP>(Op1)) {
-      if (Op1F->isNullValue())
-        return ReplaceInstUsesWith(I, Op1);
+      // TODO: If Op1 is zero and Op0 is finite, return zero.
 
       // "In IEEE floating point, x*1 is not equivalent to x for nans.  However,
       // ANSI says we can drop signals, so we can do this anyway." (from GCC)
       if (Op1F->isExactlyValue(1.0))
         return ReplaceInstUsesWith(I, Op0);  // Eliminate 'mul double %X, 1.0'
     } else if (isa<VectorType>(Op1->getType())) {
-      if (isa<ConstantAggregateZero>(Op1))
-        return ReplaceInstUsesWith(I, Op1);
+      // TODO: If Op1 is all zeros and Op0 is all finite, return all zeros.
 
       if (ConstantVector *Op1V = dyn_cast<ConstantVector>(Op1)) {
         if (Op1V->isAllOnesValue())              // X * -1 == 0 - X